Possibility of the economical utilization of forests in the radioactive contaminated areas depends on compliance of the radionuclide activity concentrations in wood with the hygiene norms or national standards that are established by the governments or regulators. Since such regulations consider wood as a whole, development of the sampling methods for assessment of compliance of wood to the norms or standards requires the adequate addressing the issues related to heterogeneity of the radionuclide distributions within the tree trunks.

In this paper we present spatial distributions of the ⁹⁰Sr and ¹³⁷Cs activity concentrations in the trunk wood of mature Scots pine (Pinus sylvestris L.) trees in the Chernobyl exclusion zone in the late stage (30 years) after the deposition. Four 52–53 year old model trees were sampled in the forest stand located in approximately 5 km from the accidental nuclear reactor. The radionuclide concentrations were measured in 156 wood samples collected from the wood disks cut off the tree trunks at the set of heights. To address variability of the tree sizes and radionuclide concentrations between the individual trees, we applied the corresponding relative indices enabling identification of the general patterns of the spatial distributions of ⁹⁰Sr and ¹³⁷Cs. We demonstrated significant differences in bioavailability and distribution trends between the studied radionuclides. ¹³⁷Cs is translocated to the younger parts of the tree trunk, while the ⁹⁰Sr concentrations are higher in heartwood and in senescing tissues, which is explained by the different chemical properties of Cs and Sr and by different physiological roles played in plant development by their chemical analogs and major plant nutrition elements, Ca and K respectively. In this reason, the principal distribution patterns of the studied radionuclides in the trunk wood do not significantly change with time, and the results of our study generally are in good agreement with those obtained in the earlier stage after the deposition. The above trends are clearly expressed in both radial and longitudinal directions and result in systematic deviation of the concentrations estimated based on core sampling from the average concentrations in the whole tree trunk.

在放射性污染地区进行森林经济利用的可能性取决于木材中放射性核素活度浓度是否符合政府或监管机构制定的卫生规范或国家标准。由于此类法规从整体上考虑了木材，因此开发用于评估木材是否符合规范或标准的采样方法要求充分解决与树干内放射性核素分布不均匀性有关的问题。

在本文中，我们介绍了沉积后后期（30年）切尔诺贝利禁区的成熟苏格兰松（Pinus sylvestris L.）树树干木材中⁹⁰ Sr和¹³⁷ Cs活性浓度的空间分布。在距离事故核反应堆约5公里的森林林中采样了四棵52-53年的老树。在从海拔一定高度的树干上切下的木盘中收集的156个木样品中测量了放射性核素的浓度。为了解决各树之间树木大小和放射性核素浓度的差异，我们应用了相应的相对指数，从而能够确定⁹⁰的空间分布的一般模式。Sr和¹³⁷ Cs。我们证明了所研究的放射性核素之间在生物利用度和分布趋势方面存在显着差异。¹³⁷ Cs转移到树干的下部，而⁹⁰ Cs转移到树干的^下部心材和衰老组织中的Sr浓度较高，这可以通过Cs和Sr的不同化学性质以及其化学类似物和主要植物营养元素Ca和K在植物发育中发挥的不同生理作用来解释。因此，所研究的放射性核素在树干木材中的主要分布模式不会随时间发生显着变化，我们的研究结果通常与沉积后早期获得的结果吻合良好。以上趋势在径向和纵向上都清楚地表示出来，并且导致基于核心采样估计的浓度与整个树干的平均浓度的系统偏差。